This invention relates to a method for measuring an optimum seeking time, taking time for settling a magnetic head into account, and an inspection apparatus using this measuring method. More particularly, in inspecting a magnetic disk or magnetic head, with respect to seeking time required when positioning the magnetic head at a target track and reading/writing data from/to the track, the invention relates to a method for measuring an optimum seeking time, taking time for settling a magnetic head into account, wherein the method can improve inspection throughput by measuring an optimum value of seeking time, taking time for settling a magnetic head into account, and setting the measured seeking time as a seeking time in the inspection of the magnetic disk or magnetic head.
In the inspection of a magnetic disk or magnetic head, when the magnetic head seeks a target track from its predetermined load position or the current track position, unless the vibration of an actuator (such as a voice coil motor) excited by a seek operation must attenuate, the magnetic head also vibrates without being stabilized in position. Therefore, a seeking time including a latency (settling time) until attenuation of the vibration of the magnetic head (actuator) is set and seeking to a target track is performed.
In particular, for a seek operation of a head under open control, the magnetic head is accelerated to a maximum speed from the load position or the current track position and, then, attenuated and positioned at a target track. In this case, the seeking time of the magnetic disk is typically defined as the sum of the positioning time until the head has been stopped, positioned at the target track, and the latency (settling time) until the vibration of the actuator has attenuated after the stop and positioning of the head.
The time until the head has been stopped and positioned in a seek operation varies with a position at which the seek is to start and a distance to the target track. A mechanical subsystem such as an arm for seeking of the head generally has a high frequency vibration proper to the mechanical subsystem. The settling time varies with the mechanical relation between the magnetic head (magnetic head assembly) and the mechanical components such as a head carriage and a spindle on which the magnetic head is placed. Moreover, the settling time also depends on aging of a driving part for the head carriage and of the mechanical subsystem.
As for the settling time, a driving technique using feed forward control that suppresses resonance of the mechanical subsystem and shortens a seeking time has been developed and already known publicly, for example, in Japanese Laid-Open Patent Application No. 2006-202368.
Conventionally, the settling time in a seek operation under open control is set at about, e.g., 50 msec, a maximum time required for ensuring the settling plus a margin, based on which, a seeking time is determined. According to this, inspection of a magnetic disk or magnetic head is performed. However, when the settling time is set at about 50 msec, the inspection is inefficient because of a long seeking time.
If a settling time shorter than 50 msec is selected, however, there is a problem that the selected settling time may be exceeded depending on conditions of the mechanical components such as the head carriage and the spindle on which the magnetic head was placed, aging of the driving part for the head carriage and of the mechanical subsystem, and replacement of the driving part for the head carriage, etc.